This application claims the priority of Korean Patent Application No. 2001-62077, filed Oct. 9, 2001 in the Korean Intellectual Property Office, which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a micro mirror device for changing the reflection path of incident light by a micro mirror, and a projector employing the same, and more particularly, to a micro mirror device that can slant with regard to a plurality of rotation axes and thus realizes color images without color wheel, and a projector employing such a micro mirror device.
2. Description of the Related Art
In general, a micro mirror device includes a plurality of micro mirrors actuated by an electrostatic attraction, and changes the reflection path of light by changing the reflection angle according to the inclination angle or direction of each micro mirror. Such a micro mirror device can be applied to an image display of a projection television and optical scanning devices used in a scanner, a copy machine or a facsimile. In particular, the micro mirror is two dimensionally arranged equal to pixels in number, being used in an image display device, and further produces an image by individually actuating each micro mirror in response to image signals for pixels and then determining the reflection angle of light.
Referring to FIG. 1, a conventional micro mirror device 115 includes a substrate 100; a pair of address electrodes 101 and a pair of bias electrodes 102 facing each other on the substrate 100; a micro mirror 106 supported by posts 105; and torsion hinges 110 that is installed between the micro mirror 106 and the posts 105, and given torsion when the micro mirror 106 is inclined. When voltage is applied to the bias electrodes 102, the voltage is transmitted to the micro mirror 106 via the posts 105 and the torsion hinges 110. Also, if voltage is applied to one of a pair of address electrodes 101, an electrostatic attraction is generated due to a difference in an electric potential between the one address electrode 101 and the micro mirror 106, and thus, the micro mirror 106 rotates due to the electrostatic attraction with regard to the torsion hinges 110. To the contrary, if a difference in the electric potential,disappears between the address electrode 101 and the micro mirror 106, the micro mirror 106 returns back to its original position, i.e., it does not slant in a certain direction and balances itself, due to the restoring force of the torsion hinges 110. Here, it is determined that the micro mirror 106 is switched ‘on’ for a predetermined color in the event that the micro mirror 106 slopes in a certain direction with regard to the torsion hinges 110, and the micro mirror 106 is switched ‘off’ for the predetermined color in the event that the micro mirror 106 slopes in the opposite direction with regard to the torsion hinges 110.
FIG. 2 is a view of a projector employing a conventional micro mirror device as illustrated in FIG. 1. Referring to FIG. 2, a beam is emitted from a light source 120, focused by a first condenser 122, and incident upon a color wheel 125. Here, a color image is realized by sequentially illuminating beams of three colors, i.e., R(red), G(green), B(blue) beams, on the micro mirror device 115 by rotating the color wheel 125 at high speed. That is, the R, G, B beams pass through the color wheel 125 and a second condenser 127, sequentially, and are then incident upon the micro mirror device 115 having the micro mirrors 106 equal to pixels in number. Then, when the micro mirror device 115 is switched ‘on’ or ‘off’ in response to an image signal for each pixel, and each micro mirror 106 is inclined in a certain direction, a color beam corresponding to each pixel is reflected on the micro mirror 115 at a certain angle and travels toward a projection lens unit 133. Next, the beam is enlarged by the projection lens unit 133 and forms an enlarged image on a screen 135.
At this time, the color wheel 125 rotates at high speed, which would make noise and the color wheel 125 to operate unstably. Further, it is impossible to rotate the projector beyond a predetermined speed due to its mechanical limitation, thereby causing color breakup. Also, light may be lost at the filter border of the color wheel 125, and therefore, light must be concentrated to a very small sized beam to prevent this problem. However, since there is a limitation in reducing light to a beam size, it is impossible to completely prevent a loss in light. Further, a color wheel is very expensive, thereby increasing manufacturing cost.